In industry, it is often necessary to clean aluminum surfaces for a variety of purposes, such as preparation for paint or for a conversion coating. Satisfactory treatment requires that any dirt and lubricant used in the aluminum forming process be removed before proceeding with additional steps.
Alkaline and acid cleaners have found wide use in the cleaning of aluminum. Acid etching and cleaning with, for example, hydrofluoric acid gives good results producing clean, mirror bright surfaces. However, the use of acids for cleaning present safety and effluent problems and necessitates the use of stainless steel for the cleaning equipment. Alkaline cleaners are thus favored in the aluminum forming and processing industry.
The accumulation of oils in cleaning solutions presents a threefold problem. Oils make metal cleaning more difficult as the capacity of the surfactants to emulsify oil becomes limited. Second, the oils in alkaline baths may saponify and contribute to foaming. Lastly, subsequent treatment of the bath effluent must separate out the emulsified oils prior to discharge. Higher treatment levels of surfactants are often used to remedy the problem of insufficient cleaning due to the presence of the oils. This not only increases the cost of the treatment but also the cost of cleaning treatment prior to effluent discharge.
Virtually any material which is capable of removing oil contamination from an aluminum surface will possibly remove some aluminum. This circumstance, particularly when coupled with the economic necessity of recycling the cleaner bath, will cause ever increasing amounts of aluminum in the bath. At some point, these insoluble aluminum compounds will drop out of the cleaning solution in the form of a sludge which, if left unchecked, will redeposit as a film or smut on the just cleaned aluminum.
The present inventor has found a way of lessening these problems by discovering a novel cleaner composition which provides good cleaning of aluminum surfaces while also providing fast oil splitting with no oxide build-up on the aluminum surface.